Reduction in left ventricular (LV) size (ventriculoplasty) by either LV aneurysm repair or partial ventriculectomy has been proposed as surgical treatment for congestive heart failure (CHF). Although results with both aneurysm repair and partial ventriculectomy have been mixed, a quantitative mechanical analysis of ventriculoplasty should allow the design of new surgical procedures that improve ventricular function. Changes in ventricular wall stress are believed to be stimuli for growth and remodelling. Thus, it is likely that surgical aneurysm repair is successful when it results in a reduction in wall stress, a subsequent improvement in border zone material properties and improvement in ventricular function. This proposal will build upon previous measurement of regional stress and ventricular function after aneurysm plication in the sheep aneurysm model. It will measure regional LV material properties before and after aneurysm repair with a biaxial stretching apparatus. Those ex vivo measurements will be confirmed from magnetic resonance measurements of regional cardiac deformation which in conjunction with knowledge of regional cardiac architecture and previously developed finite element techniques will be used to calculate regional in vivo cardiac material properties. With knowledge of myocardial material properties, the effect of three types of aneurysm repair, including plication, patch aneurysmorraphy, and radiofrequency (RF) infarct heating, on regional stress and global function will be calculated from finite element simulations. Model simulations will be validated by direct in vivo measurement of end-systolic and diastolic pressure-volume relationships, as well as magnetic resonance imaging (MRI) tissue tagging of regional 3-D myocardial strain components. Finally, the effect of aneurysm repair on border zone stress will be correlated with PET measurements of myocardial collagen and regional blood flow. These studies will help to identify the effect of ventriculoplasty in the failing heart. The long-term goal is to use experimental and theoretical models to design new surgical procedures for left ventriculoplasty that will improve ventricular function.